Construction board

ABSTRACT

The present application provides wood fiberboard comprising wood fibers bound together with a binder polymer resin that imparts additional strength and moisture resistance. As well, the fiberboard incorporates a thermal fire suppressing inorganic expandable flake graphite and sodium silicate component to render the fiberboard to be non-combustible and fire resistant. As well, a manufacturing process for adding the inorganic graphite and polymer resin binder into the fiberboard and applying the silicate onto the fiberboard is provided.

FIELD

The present disclosure relates to construction boards, in particularfiberboards.

BACKGROUND

Fiberboard (cellulosic fiber)—structural and decorative—is afibrous-felted, homogeneous panel made from ligno-cellulosicfibers—usually wood—which has a density of less than 31 lb/ft3 (497kg/m3), but more than 10 lb/ft3 (160 kg/m3). Fiberboard is characterizedby an integral bond which is produced by interfelting the fibers, butwhich has not been consolidated under heat and pressure as a separatestage in manufacture. Other materials may be added to fiberboard duringmanufacture to improve certain properties of the produced panel such aswell known waxes to provide moisture resistance and well known plantderived starches for fiber bonding to impart degrees of strength. It isalso well known in the long history of the manufacture of wood producedfiberboards that many sectors of building related projects are wellsuited for wood fiber boards that impart added thermal insulationqualities, sound suppression benefits, as well as providing for aneconomical construction cover board. For example, fiberboards are easyand light to install and may be used as interior wallboards or asexterior sheathing. Although there have been numerous advances in thehistory of fiberboard production in these areas there are some seriousshortcomings that are inherent in the present state of the art. Forexample, the following are issues of concern with current constructionboards and fiberboards:

-   1) Wood fiberboards are flammable in nature and must not be left    exposed under existing building code requirements; 2) Wood    Fiberboards are susceptible to moisture degradation due to mold and    organic decay and must be treated to meet existing building code    requirements;-   3) Wood fiberboards are generally weak in strength as compared to    other construction cover boards where structural stability is    required; and-   4) Wood fiberboards are not smooth in composition and readily    release fibers when handled or lightly abraded during standard    installation procedures and are not considered as acceptable    candidates for architectural finishes such as paint.

Over the past several years, alternative materials to commodity gradefiberboards have become available, including gypsum boards, orientedstrand boards (OSB), expanded polystyrene (EPS) and polyisocyanurateboards (Polyiso). Due to these alternative materials, demand forfiberboard has decreased. For example, production capacity of fiberboardin North America has been reduced by 37.5% over the last 5 years.However, these alternative materials have their own challenges and areless eco-friendly than fiberboard.

SUMMARY

The present invention relates to a wood fiberboard comprising woodfibers bound together with a binder polymer resin that impartsadditional strength, moisture resistance and incorporating a thermalfire suppressing expandable flake inorganic graphite and sodium silicatecomponent to render the fiberboard to be non-combustible.

The invention here described discloses a method of substantiallyimproving the fire resistance properties of a Fiberboard (Cellulosicfiber) homogenous panel by the admixture during the manufacturingprocess of certain known intumescent and binding materials in such a waythat a significant and unexpected improvement in the properties of thefiberboard composition may be achieved. In fact the unexpectedimprovements rival thermal resistance and fire protection propertiesthat are only generally achieved by well known inorganic constructionboards such as Dens glass, gypsum and concrete wallboards (Drywall)

In order to address the shortcomings addressed in the current state ofart mentioned above, research was carried out to develop a process wherethe admixing of preferred components could be carried out in thestandard manufacturing methods currently considered as the state of theart in the manufacture of said fiberboards. The research investigated:

-   (a) A water borne polymer binder that can be added to the present    manufacturing process so as to impart additional strength as well as    impart water resistance. This polymer binder would be implemented in    a similar manner and in a similar position as the existing current    art of using the aforementioned waxes and starches.-   (b) A known intumescent and/or fire retardant that would also be    compatible to the existing current art of fiberboard production.-   (c) A preferred method of surface treatment to the face of the    fiberboard so as provide for a smooth and acceptable finish that    incorporated the use of an inorganic sodium silicate to increase    strength and fire resistance.

In the present application, the terms “fiberboard” and “constructionboard” may be used interchangeably.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below with reference to thefollowing drawings:

FIG. 1 is a block diagram illustrating a manufacturing system forproducing a construction board product according to one embodiment ofthe present application;

FIG. 2 is a block diagram illustrating a continuation of themanufacturing system for producing the construction board productaccording to the one embodiment of the present application;

FIG. 3 is a graph illustrating the mean furnace temperature during afull wall burn test of a sample construction board having 30% ofgraphite by weight according to an embodiment of the presentapplication;

FIG. 4 is a graph illustrating the mean furnace temperature during afull wall burn test of a sample construction board having 15% ofgraphite by weight according to an embodiment of the presentapplication;

FIG. 5 is a graph illustrating the unexposed face maximum temperatureduring a full wall burn test of a sample of construction board of thepresent application;

FIG. 6 is a graph illustrating the unexposed face average temperatureduring a full wall burn test of a sample of construction board of thepresent application;

FIG. 7 is a graph illustrating the furnace pressure during a full wallburn test of a sample of construction board of the present application;

FIG. 8 is a graph illustrating the surface temperature of a conventionalfiberboard subjected to a heat test;

FIG. 9 is a graph illustrating the surface temperature of a fiberboardhaving a to silicate coating subjected to a heat test;

FIG. 10 is a graph illustrating the surface temperature of a fiberboardcomprising graphite according an embodiment of the present applicationsubjected to a heat test; and

FIG. 11 is a graph illustrating the surface temperature of a fiberboardcomprising graphite according an embodiment of the present applicationsubjected to a heat test.

DETAILED DESCRIPTION

In a first aspect of the present disclosure, a fiberboard composition isprovided comprising a plurality of ligno-cellulosic fibers and aninorganic expandable graphite in an amount suitable for providing fireresistance. The ligno-cellulosic fibers may be wood-based, cardboard, orany other organic ligno-cellulosic fiber known to one skilled in theart. The inorganic expandable graphite forming part of the fiberboardcomposition provides fire-resistance properties. The inorganicexpandable graphite may not expand at temperatures less than about 240°C. In some embodiments, the inorganice expandable graphite may notexpand at temperatures less than about 220° C. A suitable inorganicexpandable graphite is produced by Asbury Carbons and sold under theproduct ID Expandable Graphic Grade 1722HT (previously product numberRD18702 HT). In one embodiment, the fiberboard comprises between 15% to30% of graphite by weight. In other embodiments, the content of graphitein the fiberboard may be larger, for example up to 60% of graphite byweight. The graphite in the fiberboard improves the fire resistanceproperties of the fiberboard. For example, the fiberboards of thepresent application meet and exceed fire-resistance ratings according toCanadian and International standards. Due to the fire-resistanceproperties of the fiberboard, it may be used in various industries andapplications, for example in interior home and building construction aswell as for exterior sheathing of structures.

The fiberboard composition may further comprise a waterborne polymerbinder resin in an amount suitable for providing water resistance.Various types of waterborne polymer binder resins may be used. Forexample, this waterborne polymer binder resin may be selected from thegroup consisting of: latex, natural rubber, gutta-percha,styrene-butadiene rubber, styrene-isoprene rubber, polyisoprene,polybutadiene, polychloroprenes, organic polysulphides, butyl rubber,halogenated butyl rubber, chlorinated polyethelene, chlorosulfanatedpolyethylene, ethylene-propoylene rubber, butadiene acrylonitrilecopolymers, polyvinyl acetate, vinyl-acrylic, styrene-acrylic, and allacrylic polymers, or other waterborne polymer binder resins known to oneskilled in the art. The use of the polymer binder resin instead of astarch binder provides a fiberboard with increased strength properties.Due to the increased strength of the fiberboard product of the presentapplication, the fiberboard products may be used in various industriesfor multiple applications, including roofing systems, exterior siding,and sound proofing.

The fiberboard composition may further comprise a silicate for enhancingfire resistance. This silicate may be around 10% water-based and may beselected from the group consisting of sodium silicate and potassiumsilicate.

It is here disclosed a novel process that allows the admixing of certainknown polymer binder formulations as well as the inclusion of knowninorganic intumescent graphite particles in the present state of the artin the manufacturing of Fiberboard (Cellulosic).

While various types of polymeric binders were found to be effective inproviding the required strength and water resistance that included awide range of latexes well known to the art that include dispersions ofnatural rubber, gutta-percha, styrene-butadiene rubber, styrene-isoprenerubber, polyisoprene, polybutadiene, polychloroprenes, organicpolysulphides, butyl rubber, halogenated butyl rubber, chlorinatedpolyethelene, chlorosulfanated polyethylene, ethylene-propoylene rubber,butadiene acrylonitrile copolymers, polyvinyl acetate, vinyl-acrylic,styrene-acrylic, all acrylic polymers and the like. For propertiesneeded to achieve the desired requirements, the preferred binder wasfound to be included in the class of elastomeric styrenated acrylic inwhich the proportion of styrene to methyl acrylic acid between 10/90 and20/80 and the glass transition temperature of +5° C. or higher asproduced by Ona Polymers of Garland, Tex. USA. The ability to increasestrength and water resistance was achieved by direct in line addition ofapprox: 2-3 gals per minute into the pulp slurry during the manufactureof the fiberboard as it was being formed just ahead of the forming linepresses.

While various types of known fire retardants and inorganic intumescentswere trialed including APP, diammonium salts, monoamonium salts,borates, and boric acid, the preferred inorganic intumescents wasdiscovered to be expandable graphite as produced by Asbury Carbons andSodium Silicate as produced by PQ Corporation which could be readilydispersed through the existing and current art of fiberboard production.

The wood fiber used in the present method is acquired throughconventional methods of processing recycled wood. For example, recycledwood products may be cut up into wood chips and processed usingconventional processes to remove any foreign materials and otherimpurities. Such a conventional process may include use of a belt andmagnet conveyor to remove any metallic foreign materials from the woodchips. Next, the wood chips may be treated using conventional processesfor cleaning and treating the wood chips.

As shown in FIG. 1, there is provided one embodiment of a manufacturingsystem 100 for producing the construction board of the presentapplication. In this embodiment, the system 100 includes a machine chest102, a constant level box 104 and a head box 108. The machine chest 102contains a mixture of the processed and/or treated wood fiber and water(for example, also referred to herein as wood pulp slurry). Duringmanufacturing graphite is added into the machine chest 102 at asubstantially constant rate. This allows the graphite to evenly mix withthe wood fiber pulp and water mixture prior to the graphite wood fibermixture entering the head box 108. For example, the graphite may beintroduced into the machine chest 102 at a constant rate of ten (10)pounds of graphite per minute. The graphite may be added into themachine chest 102 manually or by some automated system or component (notshown). In alternative embodiments, the graphite may be introduced at adifferent location during the manufacturing process, such as at the headbox 108 or prior to the machine chest 102.

The graphite wood fiber mixture previously combined in the machine chest102 is moved via the constant level box 104 using a pump 106 into thehead box 108. The constant level box 104 recirculates any overflow backto the machine chest 102. In some embodiments, a coloring agent is addedto the graphite wood fiber mixture using a coloration device 103 suchthat the finished product will have a particular color. As well, wateris circulated into the head box 108 by a dilution device 105 to providea high water content mixture.

The graphite wood fiber mixture is then evenly distributed onto theformation table 110, which has a flat wire mesh surface. At the entrypoint of the formation table 110 (and after mixing with water in thehead box 108), the graphite wood fiber mixture is approximatelycomprised of 99% water and 1% of combined wood fiber and graphite. Thegraphite wood fiber mixture is moved along the formation table 110towards a plurality of rollers 118. Prior to reaching the plurality ofrollers 118, water in the graphite wood fiber mixture is filtered out ofthe mixture through the wire mesh on the formation table 110 and intothe water canal 116. As well, water may be further removed from thegraphite wood fiber mixture using a low vacuum 112 and a high vacuum 114along the formation table 110. After the removal of the water using thelow and high vacuums 112, 114, the graphite wood fiber mixture isapproximately comprised of 70% water and 30% of combined wood fiber andgraphite. The graphite wood fiber mixture is then passed through aplurality of rollers 118 which flatten the mixture to a predeterminedthickness. An overhead vacuum system 111 removes moisture and water fromthe graphite wood fiber mixture while it is being passed along theformation table and while it is being flattened. As well, during theflattening step, further water is removed from the graphite wood fibermixture, the water falling into the water canal 116. After flattening,the mixture is now formed into a semi-rigid board on the formation table110. An optional coating may be applied to the semi-rigid board at thisstage from coating shower system 126. The semi-rigid pre-fiberboard iscut into predetermined sized pieces by the cross-cutter 120 and then issent to a dryer system 200 for drying and hardening. At this stage, thesemi-rigid pre-fiberboard is approximately comprised of 48% water and52% of combined wood fiber and graphite. Any excess graphite wood fibermixture falls into a pulper 122 and is stored in a reserve chest 123.

FIG. 2 illustrates the dryer system 200 as part of the overallmanufacturing system of the fiberboard shown in FIG. 1, according to theone embodiment of the invention. The semi-rigid board continues onto oneor more conveyors 202 into one or more dryers 204. The dryers 204operate to remove the majority of the remaining water that is in thesemi-rigid fiberboard. The dryers 204 remove a significant amount ofwater such that the dried fiberboard leaving the dryers 204 isapproximately comprised of 5% water and 95% of combined wood fiber andgraphite. The dried fiberboard exits the dryers 204 onto one or moreconveyors 205 and may be cut into predetermined sized pieces by one ormore saws 206. The fiberboard may be cut in any size of board. After thedried fiberboard has been cut, the fiberboard proceeds onto a conveyor208 to receive final treatments. For example, the surface of thefiberboard may be smoothed by a calender 210, the surface of thefiberboard may receive a polymer coating applied by a coating device 212and the surface of the fiberboard may be laminated by a laminationdevice 214. After receiving the one or more final treatments, thefinished fiberboard product may be stored. The finished fiberboard maybe cut into boards having generally the dimensions 4 feet×8 feet×½ feet.

The fiberboard may be cut into any size and the thickness of thefinished fiberboard may vary depending on the intended end useapplication.

During the trials there were a number of obstacles that needed to beovercome.

1. Polymer Binder

-   (a) Although a waterborne polymer emulsion was compatible with    existing manufacturing methods during the process it was found that    the surfactants in the polymers had to be re-worked and cross linked    as they were impacting water resistance due to their very nature of    being hydrophilic. A new proprietary surfactant had to be added to    the polymer binder with a cross linking agent WB31B(metal complex)    as produced by Federal Process Corp that reacts only after the    formulation soaks into the wood fiber and the water evaporates.    Cross linking the surfactant destroys its ability to attract water    and preserves depth of penetration better than solvent-based    systems.-   (b) The polymer binder had to be adjusted to a cationic ph of 6 or    less so as bind to the cellulosic fiber as the fiber carried an    anionic charge to enhance attraction.-   (c) The polymer binder may be added to the machine chest 102 or may    be added to the head box 108, for mixing with the wood fiber slurry.    As well, the polymer binder may be added at another point during the    manufacturing process. The use of the polymer binder rather than    conventional binders (e.g. starch) results in a stronger fiberboard    product. Due to the increased strength properties of the fiberboard    of the present application, it may be used in various industries and    for various applications that conventional fiberboard could not be    used, for example for roofing applications which require a certain    level of structural strength, for example, to permit walking on top    of fiberboard.-   (d) The percentage of the polymer binder in the fiberboard was    trialed approximately between 0% to 15%.

TABLE 1.1 TC12-xxxx (ID #) 173G 174I 174H 17OA 174J Binder Starch StarchStarch polymer polymer % solids of Binder N/A N/A N/A   55%   55% Weightof Binder 2.07% 2.12% 2.02%  1.91%  1.93% Wood Fiber 28.05% 27.80%27.25% 28.08% 27.92% Water 69.88% 68.98% 67.02% 69.83% 68.73%Crosslink-WB31B 0.00% 0.00% 0.00%  0.18%  0.18% Wax 0.00% 1.09% 3.70% 0.00%  1.24% Total 100.00% 100.00% 100.00% 100.00%  100.00%  Wt. Before 8.5640 (g)  7.9883 (g)  8.4619 (g) 8.4225 (g)%  8.0680 (g) water (g)Wt. After 2 Hr (g) 14.5257 (g) 12.6892 (g) 12.3866 (g) 11.3183 (g)10.2342 (g) Absorption 2 Hr 69.61% 58.55% 46.38% 34.38% 26.85% (%) Wt.Before  8.3347 (g)  8.3696 (g)  8.5919 (g)  8.8394 (g)  8.1127 (g) water(g) Wt. After 4 Hr (g) 34.9321 (g) 14.8635 (g) 14.7384 (g) 11.9293 (g)10.8069 (g) Absorption 4 Hr 319.10% 77.59% 71.54% 34.96% 33.21% (%)

Table 1.1 illustrates a comparison between conventional fiberboardshaving starch as a binder and fiberboards of the present applicationwhich utilize polymer as a binder. The example fiberboards 173G, 174Iand 174H each utilized starch as a binder. Starch is a highlycombustible material. Fiberboards 173G, 174I and 174H have generally thesame percentages of wood fiber, water and weight of the starch binder.The characteristics of fiberboards 173G, 174I and 174H differ in thepercentage of wax used, with 173G having 0%, 174I has 1.09% and 174Hhaving 3.70%. The use of wax in the fiberboards decreases to the waterabsorption percentage after 2 hours and after 4 hours, with the highestamount of wax 3.70% in fiberboard 174H providing the lowest waterabsorption rates.

As shown in Table 1.1, Fiberboards 170A and 174J of the presentapplication utilize the above-described polymer as a binder. Thefiberboards 170A and 174J have generally the same percentages of solidsof the polymer binder, wood fiber, crosslink-WB31B and water, andgenerally the same weight of the polymer binder. The characteristics ofthe fiberboards 170A and 174J differ in the percentage of wax used, with170A having 0% and 174J having 1.24%.

When comparing conventional fiberboard 173G with the fiberboard 170Aaccording to the present application, where both have no wax component,it is shown that the water absorption percentage (2hours and 4 hours) isreduced significantly when the binder of the fiberboard is the polymerbinder having the new proprietary crosslinking agent WB31B of thepresent application. For example, the 4 hour water absorption percentageof the fiberboard 170A of the present application is 34.96% in contrastto the conventional fiberboard 173G which has a 4 hour water absorptionpercentage of 319.10%.

Fiberboard 174J of the present application differs from fiberboard 170Ain that it contains 1.24% of wax. The introduction of the wax does notprovide a significant decrease in water absorption percentages, as the 4hour water absorption percentage of the fiberboard 174JA of the presentapplication is 33.21% and the 4 hour water absorption percentage of thefiberboard 170A (without wax) of the present application is 34.96%.

Conventional fiberboards 173G, 174I and 174H are made with a starchbinder and include a wax component in order to reduce percentages ofwater absorption. However, one problem with using starch and wax infiberboards is that these materials are highly flammable. In the presentapplication, the fiberboards are manufactured without starch and withoutwax, making them less flammable than conventional fiberboards. Insteadof a starch binder, the fiberboards of the present applicationmanufactured with a polymer binding, which results in decreased waterabsorption percentages than the conventional starch binder basedfiberboards.

2. Expandable Graphite

-   (a) Expandable graphite is known as an intercalation compound, the    expansion factor and ability to expand is determined by temperature    gradients. It is thus desirable that the expansion occur rapidly    once the material reaches a certain critical value. Most commonly    the temperature at which such expansion commences is within the    range of 150° C. to 220° C. The production of Fiberboard requires    travel through ovens 204 (FIG. 2) in the drying process where    temperatures exceed 240° C. It was imperative that we have the    manufacturer of the graphite produce graphite with higher    temperature limits. Asbury Carbons a world leader in carbon mining    was able to formulate a new high temperature reactive graphite that    met our requirements and it has been commercially branded as    Expandable Graphic Grade 1722HT (previously identified as RD 18702    HT). Accordingly, with the use of the expandable graphic having    higher temperature limits, particularly Grade 1722HT, this obstacle    was overcome. Table 1.2 shows the typical properties of expandable    graphite at different grade levels as indicated and sold by Asbury    Carbons. As previously discussed, for the present application, the    preferred grade of expandable graphite is 1722HT as the onset    temperature is very high (220-230° C.); and will work with furnace    temperatures in the 240° C. range.

TABLE 1.2 Asbury Carbons - Typical Properties Expandable Graphite

3772 >300 ≥98 0.9 3.1 300:1 5-10 180-200 1721 >300 ≥98 0.9 3.5 300:1 1-6180-200 3721 >300 ≥95 0.9 3.5 290:1 5-10 180-200 1722 >300 ≥95 0.9 3.5290:1 1-6 180-200 3335 >300 ≥85 0.9 3.2 270:1 5-10 180-200 3577 >300 ≥850.9 3.4 270:1 1-6 180-200 3570 >180 ≥80 0.8 3.1 230:1 5-10 150-1701395 >180 ≥80 0.8 3.5 230:1 1-6 150-170 3558 >180 ≥99 0.8 3.1 210:1 5-10180-200 3626 >75 ≥80 0.6 3.0 160:1 5-10 150-170 3494 >75 ≥80 0.9 2.9 90:1 1-6 160-180 3538 <75 ≥80 1.4 2.6  60:1 5-10 200-225 1722HT >300≥95 1.6 5.0 220:1 1-6 220-230

indicates data missing or illegible when filed

-   (b) As the expandable graphite is a solid and not a liquid, this    posed a problem as to how and where to insert the required flow so    as to have correct particle distribution throughout the mass of the    fiberboard panel. This obstacle was overcome after trialing numerous    entry areas. The preferred entry point was identified at the    existing head box 108 that in fiberboard production provides the    distribution of wood fiber slurry by high volume agitation evenly    throughout the main forming line. By adding the graphite at the rate    of 10 lbs per minute at this location very uniform particle    distribution was recorded. In some embodiments, the graphite is    added to the machine chest 102 at a constant rate, prior to the head    box 108. The introduction of graphite during the fiberboard    manufacturing process as described herein results in a fiberboard    product having improved fire resistance properties.

3. Surface Treatment

The surface treatment of the face of the boards is realized bysubjecting the finished board as it came out of the dryers 204 to asurface coat of sodium silicates (case trials were done with both sodiumand potassium silicates and sodium due to its relatively inexpensivecost was chosen as the preferred method.) The surface treatment wasoptimized using a spray coat of a 10% water based solution(higher andlower concentrations in the range of 5% to 100% were trialed but theoptimum was 10%) of inorganic sodium silicate which quickly penetratedthe surface of the fiberboard and then was sent into a calender pressroller 210 to provide a suitable smooth profile for paint application.In some embodiments, the surface treatment is performed by a coatingdevice 212 after the fiberboard is sent into the calender press roller210, as shown in FIG. 2. The application of the sodium silicate wasenhanced by the addition of a high heat (450F-500F) pressure compressionroller that not only provided for a smooth surface but in doing so setthe sodium silicate due to the high temperature flash drying of thewater carrier that resulted in a smooth glass like appearance thatprovided an additional fire resistance quality that is well known inthis particular chemistry of silicates otherwise known as waterglass.

To exemplify the fire resistant characteristics of the fiberboard of thepresent application, full wall burn tests were performed. For thesetests, fiberboard made with natural pulp and comprising the graphite,polymer resin binder and the silicate coating was used. A first batch ofthe fiberboard was produced with a graphite content of 15% by weight(for example, during manufacturing the graphite may be added at a rateof 5 lbs of graphite per minute) and a second batch of fiberboard wasproduced with a graphite content of 30% by weight (for example, duringmanufacturing the graphite may be added a rate of 10 lbs of graphite perminute).

FIG. 3 is a graph of the mean furnace temperature during the CAN ULCS101-14 full wall test of fiberboard from the second batch having agraphite content of 30% by weight. The x-axis of FIG. 3 represents thetemperature of the furnace in Fahrenheit and the y-axis represents thelength of time in minutes the fiberboard burns until it reaches afailure state. For the purposes of the full wall burn test, a failurestate of the fiberboard is when the fiberboard reaches a thermal lossvalue that exceeds ASTM fireproofing standards. As shown in FIG. 3, twothermal losses occur after 35 minutes and after 40 minutes. Conventionalfiberboards subjected to a similar full wall burn test would reach athermal loss within 5 minutes. Accordingly, the fiberboard of thepresent application provides superior fireproofing qualities compared toconventional fiberboard. This improved fireproofing characteristic ofthe fiberboard of the present application is in part a result of thegraphite added to the fiberboard during manufacturing.

FIG. 4 is a graph of the CAN ULC S101-14 mean furnace temperature duringthe full wall test of fiberboard from the first batch having a graphitecontent of 15% by weight. As shown, a thermal loss occurs on the graphbetween 25 and 30 minutes. Accordingly, when comparing the full wallburn test results of the first batch of fiberboard having 15% graphiteby weight with the second batch of fiberboard having 30% graphite byweight, it is shown that the increased amount of graphite in thefiberboard resulted in an increase in time before a thermal loss eventoccurs, thereby improving the fireproofing characteristics of thefiberboard.

FIG. 5 is a graph illustrating the unexposed face maximum temperatureduring a CAN ULC S101-14 full wall burn test of a sample of constructionboard of the present application;

FIG. 6 is a graph illustrating the unexposed face average temperatureduring a CAN ULC S101-14 full wall burn test of a sample of constructionboard of the present application;

FIG. 7 is a graph illustrating the furnace pressure during a CAN ULCS101-14 full wall burn test of a sample of construction board of thepresent application.

The fiberboard (Cellulosic fiber) of the present application is renderednon-combustible due to the inclusion in its composition of a new hightemperature activated expandable graphite.

As well, the fiberboard (Cellulosic fiber) of the present applicationhas improved strength characteristics and water resistance propertiesdue to the inclusion of polymer binders in its composition.

Also, the fiberboard (Cellulosic fiber) of the present application has asodium silicate (waterglass) surface treatment and compressed profilethat results in a smooth and paint ready surface with inherent fireresistant properties.

Thermal testing was conducted on sample fiberboards to illustrate theeffects that the silicate and graphite, alone and in combination, haveon the thermal resistant properties of the fiberboard of the presentapplication. As a baseline, a thermal test was conducted on a standardconventional fiberboard. For each of the thermal tests, the furnacetemperature was maintained at an approximate temperature of 1500° F. Onthe graphs in FIGS. 8 to 11, where the unexposed surface temperature ofthe board is shown to surpass the furnace temperature is an indicationof a thermal loss event, which may considered as a failure point of thefiberboard that is being subjected to heat.

FIG. 8 illustrates the results of such the thermal test on aconventional fiberboard. As shown, the unexposed surface temperature ofa conventional fiberboard rapidly rises to just over 1400° F. andreaches a failure state in less than approximately 2 minutes.

FIG. 9 illustrates the results of the thermal test on a fiberboardhaving a silicate coating. As previously discussed, a silicate coatingprovides fire-resistant properties to a fiberboard. In FIG. 9, theunexposed surface temperature rises to approximately only 400° F. after30 minutes of exposure, despite the furnace temperature beingapproximately 1500° F. The fiberboard having the silicate coatingreaches a failure state at approximately between 35 and 40 minutes.Accordingly, the silicate coating on the fiberboard provides improvedthermal resistance when compared with the heat test results of theconventional fiberboard of FIG. 8 which reached a failure state within 2minutes under the same furnace temperature conditions.

FIG. 10 illustrates the results of the thermal test on a fiberboardcomprising a predetermined percentage of graphite, according to thepresent application. As previously discussed, the introduction ofgraphite during the fiberboard manufacturing process, as provided in thepresent application, improves the fire resistant properties of thefiberboard. In FIG. 10, the unexposed surface temperature rises toapproximately only 400° F. after about 35 minutes of exposure, despitethe furnace temperature being approximately 1500° F. The fiberboardcomprising the graphite reaches a failure state at approximately between40 and 50 minutes. Accordingly, the fiberboard comprising graphiteprovides improved thermal resistance when compared with the heat testresults of the conventional fiberboard of FIG. 8 which reached a failurestate within 2 minutes under the same furnace temperature conditions.

FIG. 11 illustrates the results of the thermal test on a fiberboardcomprising a predetermined percentage of graphite and having a silicatecoating, according to the present application. In FIG. 11, the unexposedsurface temperature rises to approximately only 400° F. after about 45minutes of exposure, despite the furnace temperature being approximately1500° F. The fiberboard comprising the graphite and having the silicatecoating reaches a failure state at approximately 50 to 55 minutes.Accordingly, the combination of the fiberboard comprising graphite andhaving a silicate coating provides the greatest level of thermalresistance relative to the examples provided in FIGS. 9 (fiberboardhaving silicate coating only) and 10 (e.g. fiberboard comprised ofgraphite only). As well, the combination of the fiberboard comprisinggraphite and having a silicate coating provides significant improvementof thermal resistance (e.g. failure after 50 minutes of heat exposure)when compared with the heat test results of the conventional fiberboardof FIG. 8 which reached a failure state within 2 minutes under the samefurnace temperature conditions.

Furthermore, various tests (for example, to identify thermalconductivity, water absorptiveness) were performed to compare thestandard specifications of gypsum board (for example, according to ASTM1.1.1 standard) to samples of the fiberboard of the present application.For these tests, the fiberboard samples of the present application has athickness of approximately ⅝ inches. As well, the tests were performedon samples of ⅝″ gypsum boards having water-repellent surfaces.

Tables 2.1 and 2.2 show results of thermal conductivity tests performedin accordance with the ASTM C518 standard. In Tables 2.1, the thermalconductivity of the gypsum boards is shown. The RSI value for thermalresistance is 0.08 Cm2/W for the gypsum board, the heat flow rate in themeasured area is 12.45W, and the thermal conductivity rating is R=0.48.

TABLE 2.1 Thermal conductivity on ⅝″ gypsum boards with water-repellentsurfaces (According to Standard ASTM C518) Heat flow rate in the meteredThermal Thermal Dry Sample ΔX_(Theoretical) ΔX area (Q) ΔT K resistanceat 1

resistance RSI weight Density

in (

) in (

) W ° F. BTU · po/° F. · pi² · h ° F. · pi² · h/BTU ° F. · pi² · h/BTU °C. · m²/W g lbs/pi³ ⅝″ 0.625 0.620 12.45 2.04 1.305 0.766 0.48 0.081036.08 44.28 gypsum

indicates data missing or illegible when filed

In Table 2.2, the thermal conductivity properties of sample fiberboardsof the present application are shown (for example, the fiberboard hasthe proprietary name “Starboard”). For the fiberboard #7 having thecharacteristics and properties of the present application, the RSI valuefor thermal resistance is 0.29 Cm²/W and the heat flow rate in themeasured area is 5.53W. The other tested fiberboard #8 of the presentapplication as tested had a similar RSI and heat flow rate as fiberboard#7. The thermal conductivity rating of fiberboard #7 is R=1.63 and offiberboard #8 is R=1.59.

TABLE 2.2 Thermal conductivity on ⅝″ MSL fireproof and calenderedfiberboard of the present application (According to Standard ASTM C518)Heat flow rate in the metered Thermal Thermal Dry SampleΔX_(Theoretical) ΔX area (Q) ΔT K resistance at 1

resistance RSI weight Density

in (

) in (

) W ° F. BTU-po/° F. · pi² · h ° F. · pi² · h/BTU ° F. · pi² · h/BTU °C. · m²/W g lbs/pi³ Starboard #7 0.625 0.610 5.53 2.97 0.375 2.667 1.630.29 484.36 21.04 Starboard #8 0.625 0.590 5.63 2.94 0.372 2.688 1.590.28 473.42 21.26

indicates data missing or illegible when filed

Accordingly, from the testing it is shown that the fiberboard producedaccording to the present application has improved heat resistanceproperties (e.g. RSI, heat flow rate) over gypsum boards.

Tables 3.1. 3.2 and 3.3 show results of water absorptiveness testsperformed on the gypsum board samples (Table 3.1) and the fiberboardsamples of the present application (Table 3.2 and 3.3), in accordancewith the ASTM D3285 Standard Test Method for Water Absorptiveness ofNonbibulous Paper and Paperboard (also known as the “Cobb Test”). Intable 3.1, the results of the Cobb Test for the gypsum board samples isshown, where the average absorption of the gypsum board over a 4 hourperiod was 773.64 g/m² and the average surface absorption was 3.24%.

TABLE 3.1 Cobb Test on 5/″ gypsum boards with water-repellent surfaces(white side) (test duration: 4 hours) Sample Initial weight Final weightAbsorption Surface absorption 4 hours g g g/m² % C-1 251.57 258.05651.91 2.51 C-2 213.40 221.81 846.08 3.79 C-3 211.93 220.52 864.19 3.90C-4 254.97 262.25 732.40 2.78 Average 232.97 240.66 773.64 3.24

In Table 3.2, the results of the Cobb Test for the fiberboard samples ofthe present application is shown, where the average absorption of thefiberboard over a 2 hour period was 244.22 g/m² and the average surfaceabsorption was 2.06%.

TABLE 3.2 Cobb Test on ⅝″ MSL fireproof and calendered fiberboard of thepresent application (test duration: 2 hours) Sample Initial weight Finalweight Absorption Surface absorption 2 hours g g g/m² % C-1 112.25114.51 227.37 1.97 C-2 114.79 117.03 225.35 1.91 C-3 116.41 119.06266.60 2.23 C-4 117.76 120.32 257.55 2.13 Average 115.30 117.73 244.222.06

In Table 3.3, the results of the Cobb Test for the fiberboard samples ofthe present application is shown, where the average absorption of thefiberboard over a 4 hour period was 303.57 g/m² and the average surfaceabsorption was 2.72%.

TABLE 3.3 Cobb Test on ⅝″ MSL fireproof and calendered fiberboard of thepresent application (test duration: 4 hours) Sample Initial weight Finalweight Absorption Surface absorption 4 hours g g g/m² % C-1 108.60111.79 320.93 2.85 C-2 105.59 108.68 310.87 2.84 C-3 110.94 113.59266.60 2.33 C-4 107.50 110.64 315.90 2.84 Average 108.16 111.18 303.572.72

Accordingly, from the testing it is shown that the fiberboard producedaccording to the present application has reduced absorption propertiesand characteristics (absorption and surface absorption percentage) overgypsum boards.

Table 4 shows results of an absorption by water immersion test performedon the fiberboard samples of the present application, according to theASTM C209 Standard (Standard Test Methods for Cellulosic FiberInsulating Board—Section 14). As shown in Table 4, after a 2 hour testduration, the average absorption percentage is 6.81%.

TABLE 4 Absorption by water immersion on ⅝″ MSL fireproof and calenderedfiberboard of the present application Sample Initial weight Final weightAbsorption Absorption 2 hours g g g % A-1 112.40 130.68 18.28 4.96 A-2109.71 128.57 18.86 5.12 A-3 113.92 134.95 21.03 5.70 A-4 116.16 158.4842.32 11.48 Average 6.81

Strength tests were also performed on the fiberboard of the presentapplication. Table 5 shows the measured results of a tensile strengthtest performed according to the ASTM C208 Standard (Section 13). Asshown in Table 5, the tensile strength perpendicular to the surface ofthe fiberboard was measured, with an average net strength of: 620.67psf, 281.53 kg and 29.72 Kpa.

TABLE 5 Tensile strength perpendicular to surface on ⅝″ MSL fireproofand calendered fiberboard of the present application Sample TEST TARENet strength Average Net strength Average Net strength Average MIN Side# psf psf psf psf kg kg Kpa Kpa psf-kg-Kpa

S-1 785 18 767 347.91 36.72 Bottom S-2 496 18 478 620.67 216.82 281.5322.89 29.72 120-55-6 Top S-3 635 18 617 279.87 29.54 Bottom

indicates data missing or illegible when filed

Tables 6.1 and 6.2 show the measured results of transverse strengthtests performed on the fiberboard of the present application, accordingto the ASTM C209 standard (Section 10). In table 6.1, the averagetransverse strength perpendicular to the board panel length of the “M”samples was 28.501 bf and the average transverse strength perpendicularto the board panel length of the “T” samples was similar with 27.831 bf.After a two week curing period, the transverse strength was measuredagain, and as shown in table 6.2, the average transverse strength of the“M” samples was 25.17 lbf and the average transverse strength of the “T”samples was similar with 24.70 lbf. In contrast, a gypsum board has astandard specification (according to ASTM 1.1.1) of transverse strengthperpendicular to the board panel length of 23.5 lbf. Accordingly, thefiberboard of the present application has an increased transversestrength compared to gypsum board.

TABLE 6.1 Transverse strength test on ⅝″ MSL fireproof and calenderedfiberboard of the present application Sample Transverse strength Average⅝″ Starboard lbf lbf 1-M

28.50 2-M 28.2 3-M

4-M 29.8 5-M 27.5 1-T 28.0 27.83 2-T 27.8 3-T

4-T 27.7 5-T

TABLE 6.2 Transverse strength test on ⅝″ MSL fireproof and calenderedfiberboard of the present application after a two week curing timeSample Transverse strength Average ⅝″ Starboard lbf lbf 1-M 25.9 25.172-M

3-M

4-M 24.2 5-M 25.4 1-T 23.7 24.70 2-T

3-T 25.6 4-T 24.8 5-T

Calculations were performed to determine the average density of thefiberboard of the present application. As shown in Table 7, for afiberboard having a generally uniform ⅝″ thickness, the average dryweight was 460.94 g and the average density is 19.91 lbs/ft³.

TABLE 7 Average density calculation of the ⅝″ MSL fireproof andcalendered fiberboard of the present application Average SampleProduction thickness Dry weight Density Natural ⅝″ Code In g lbs/pl³ 1MSL Starboard-CA 0.6155 463.10 19.94 2 MSL Starboard-CA 0.6150 461.0319.87 3 MSL Starboard-CA 0.5980 444.31 19.69 4 MSL Starboard-CA 0.6265473.71 20.04 5 MSL Starboard-CA 0.6141 462.70 19.97 6 MSL Starboard-CA0.6158 463.10 19.93 7 MSL Starboard-CA 0.6164 466.12 20.04 8 MSLStarboard-CA 0.6159 464.17 19.97 9 MSL Starboard-CA 0.6036 452.60 19.8710  MSL Starboard-CA 0.6148 458.54 19.77 Average — 0.6135 460.94 19.91

One or more currently preferred embodiments have been described by wayof example. It will be apparent to persons skilled in the art that anumber of variations and modifications can be made without departingfrom the scope of the invention as defined in the claims.

1. A fiberboard composition comprising: a plurality of ligno-cellulosicfibers; and an inorganic expandable flake graphite in an amount between10 and 50 percent by weight for providing fire resistance.
 2. Thefiberboard composition of claim 1, further comprising a waterbornepolymer binder resin in a suitable amount for providing waterresistance.
 3. The fiberboard composition of claim 1 further comprisinga silicate for enhancing fire resistance.
 4. The fiberboard compositionof claim 1, wherein said inorganic expandable graphite does not expandat temperatures less than about 240° C.
 5. The fiberboard composition ofclaim 2, wherein said water polymer binder resin is selected from thegroup consisting of: latex, natural rubber, gutta-percha,styrene-butadiene rubber, styrene-isoprene rubber, polyisoprene,polybutadiene, polychloroprenes, organic polysulphides, butyl rubber,halogenated butyl rubber, chlorinated polyethelene, chlorosulfanatedpolyethylene, ethylene-propoylene rubber, butadiene acrylonitrilecopolymers, polyvinyl acetate, vinyl-acrylic, styrene-acrylic, and allacrylic polymers.
 6. The fiberboard composition of claim 3, wherein saidsilicate is selected from the group consisting of: sodium silicate andpotassium silicate.
 7. The fiberboard composition of claim 3, whereinsaid silicate is around 10% water based.
 8. A method of making afiberboard comprising: forming a pulp slurry comprising a plurality ofligno-cellulosic fibers and water; adding of an inorganic expandablegraphite to said pulp slurry for providing fire resistance to thefiberboard; pressing said pulp slurry and said inorganic expandablegraphite to form at least one layer of pre-fiberboard composition;interfelting said layer of pre-fiberboard composition to form apre-fiberboard; and drying said pre-fiberboard.
 9. The method of makinga fiberboard of claim 8, further comprising adding of a waterbornepolymer binder resin to said pulp slurry for providing water resistanceand strength to the fiberboard.
 10. The method of making a fiberboard ofclaim 8, further comprising coating said pre-fiberboard with a silicatefor enhancing fire resistance of said fiberboard.
 11. The method ofmaking a fiberboard of claim 8, further comprising press rolling saidpre-fiberboard to limit roughness of the fiberboard.
 12. The method ofclaim 8, wherein said inorganic expandable graphite does not expand attemperatures less than about 240° C.
 13. The method of claim 8, whereinsaid inorganic expandable graphite is added at a rate of about 10 lbsper minute.
 14. The method of claim 9, wherein the waterborne polymerbinder resin is selected from a group consisting of: latex, naturalrubber, gutta-percha, styrene-butadiene rubber, styrene-isoprene rubber,polyisoprene, polybutadiene, polychloroprenes, organic polysulphides,butyl rubber, halogenated butyl rubber, chlorinated polyethelene,chlorosulfanated polyethylene, ethylene-propoylene rubber, butadieneacrylonitrile copolymers, polyvinyl acetate, vinyl-acrylic,styrene-acrylic, and all acrylic polymers.
 15. The method of claim 9,wherein the waterborne polymer binder resin is added at a rate ofbetween about 2 to about 3 gallons per minute into said pulp slurry. 16.The method of claim 10, wherein said silicate coating is selected fromthe group consisting of: sodium silicate and potassium silicate.
 17. Themethod of claim 10, wherein said silicate coating is around 10% waterbased.
 18. The method of claim 11, wherein said press-rolling isperformed under a temperature of between about 450 to about 500° F. 19.The fiberboard composition of claim 1, wherein the composition comprisesapproximately 30% of the inorganic expandable graphite by weight. 20.The fiberboard composition of claim 1, wherein the composition comprisesapproximately 15% of the inorganic expandable graphite by weight. 21.The fiberboard composition of claim 1, wherein the composition comprisesapproximately 1 to 3% of the waterborne polymer binder resin. 22.(canceled)
 23. (canceled)